{"id":"c01e0989-6ad9-4464-ab66-38780613ce07","arxiv_id":"2502.04203","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"PrSb0.3Te1.7 exhibits 97% negative magnetoresistance at 2 K and 9 T with two-fold angular anisotropy and no long-range magnetic order above 1.8 K.","lead":"PrSb0.3Te1.7, a composition of the magnetic topological material family PrSbxTe2-x, shows a very large negative magnetoresistance of 97% at 2 K and 9 T. The work maps how varying antimony and tellurium content changes crystal structure and transport, pointing toward a material for studying magnetotransport without long-range magnetic order.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Contact misalignment may contaminate the reported 97% negative MR with a Hall voltage; the paper does not report symmetrized R(+B)/R(-B) measurements.","rationale":"The reader's weakest assumption concerned the high-temperature Hall data used to infer a band-structure transformation; that is a valid concern about the interpretation, but it leaves the raw MR observation intact. The contact-misalignment artifact I identify threatens the measured MR itself, which is the paper's central claim. The paper's own statement about Hall contamination in exactly these strong-MR samples is an in-scope limitation that explicitly flags imperfect contact geometry. Given the very high zero-field resistivity (~50 Ω cm at 2 K) and the large field-induced suppression, the sample is in a regime where the Hall angle could be substantial at low temperature if the carrier density is small, so the antisymmetric contamination is not obviously negligible. The observed angular dependence, with a strong effect only when the field is perpendicular to the ab-plane, is precisely what one would expect from pickup of the in-plane Hall field by misaligned contacts, whereas the out-of-plane Hall field for H//ab would not be detected. The standard remedy, symmetrizing over field direction, is not described in the manuscript. I give credit for the reproducibility across multiple near-identical samples and the consistent two-fold anisotropy, but those do not address a systematic contact artifact. Therefore, the paper should be accepted only conditionally, pending a field-reversal or Hall-bar control. If the test shows the antisymmetric component is negligible, the raw MR observation stands, and the main residual issue would be the reader's Hall-carrier-density concern about the mechanism. My concern is not an accusation of misconduct; it is a request for a standard experimental control that the text does not demonstrate.","tokens_in":14747,"tokens_out":9952,"duration_ms":105914,"concrete_test":"Measure the longitudinal resistance of PrSb0.3Te1.7 at T = 2 K for H⊥ab at +9 T and -9 T (and at several intermediate fields), and compute the symmetric part [R(+B)+R(-B)]/2 and the antisymmetric part [R(+B)-R(-B)]/2. If the antisymmetric component at 9 T exceeds, say, 10% of the symmetric component, the reported negative MR is contaminated and is not an intrinsic longitudinal response. As a complement, repeat the angular MR scan at ±9 T; if the two-fold pattern is identical for both field directions, it is even and not Hall-like, but if the pattern flips or shifts, a contact-misalignment Hall voltage is present. Additionally, remeasure MR using a Hall-bar geometry with voltage contacts placed along the sample centerline, or perform a van der Pauw measurement, to confirm the negative MR is geometry-independent.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim is the 97% negative transverse MR in PrSb0.3Te1.7. The paper explicitly states in Section III that for samples with strong MR, 'it is difficult to obtain meaningful Hall effect data at low temperatures' because of the 'inevitable mixture of the longitudinal resistivity component.' This is an admission that the electrical contacts are not perfectly aligned. The converse contamination — a Hall voltage picked up by the longitudinal resistivity contacts — would be especially severe in a highly resistive sample where the Hall angle can become large if the carrier density drops at low temperature. The reported MR is defined using the absolute value |[ρ(H)-ρ(0)]|/ρ(0), and the paper does not mention averaging measurements at +B and -B to remove the antisymmetric Hall component. Notably, the huge effect appears only for H⊥ab, where the Hall field lies in the plane and can be collected by misaligned in-plane voltage contacts, while it is absent for H//ab, where the Hall field is out-of-plane and would not be picked up. The same contact asymmetry that corrupts the Hall data could therefore generate a spurious large negative MR. Reproducibility across multiple samples and the two-fold angular pattern are suggestive but do not rule out a systematic contact artifact. The raw observation is the load-bearing element of the paper, so this concern threatens the central claim directly, not merely the speculative mechanism.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This manuscript reports a composition-dependent study of the topological material family PrSbxTe2-x (0.05 < x < 0.91), combining structural characterization, resistivity, Hall effect, magnetization, and heat capacity measurements. The central experimental claim is that the off-stoichiometric composition PrSb0.3Te1.7 exhibits very large negative transverse magnetoresistance, reaching 97% at 2 K and 9 T for H perpendicular to the ab-plane, together with a two-fold angular anisotropy that mirrors the magnetic anisotropy. The authors propose that the negative MR arises from magnetic-field-driven modification of the electronic structure, possibly aided by the strongest orthorhombic distortion in the series, while explicitly noting that the microscopic mechanism remains unresolved.","tokens_in":15084,"tokens_out":3670,"duration_ms":40364,"significance":"If the 97% negative transverse MR is genuine, this is a noteworthy addition to the small family of materials showing large negative MR without long-range magnetic order, and it would strengthen the case for LnSbxTe2-x as a tunable platform for magnetotransport studies. The systematic composition dependence, structural phase mapping, and the observation of re-entrant tetragonal structure at very low Sb content are useful experimental contributions. However, the central observation is not yet fully established because the paper does not report symmetrized longitudinal-resistivity measurements, leaving a concrete risk that contact misalignment and Hall-voltage contamination contribute to the reported effect.","major_comments":[{"comment":"The paper does not report symmetrized measurements of the longitudinal resistivity (averaging the measured voltage at +B and -B), nor any test of contact alignment. The authors themselves state that for strong-MR samples \"it is difficult to obtain meaningful Hall effect data at low temperatures\" because of \"the inevitable mixture of the longitudinal resistivity component.\" The converse contamination, namely pickup of the antisymmetric Hall voltage by the nominal longitudinal contacts, is a real risk, and it is particularly severe for the H⊥ab configuration used to report the 97% MR, because the Hall field then lies in the ab-plane and can be collected by misaligned in-plane voltage contacts. The absence of the effect for H//ab, where the Hall field is out of plane, is exactly the pattern such a contact artifact would produce. Please provide resistivity data for both field polarities with the antisymmetric component removed, and demonstrate that the 97% MR and the angular pattern in Fig. 6 survive this procedure.","section":"Section III, Fig. 3b and the Hall-effect paragraph"},{"comment":"The carrier density and carrier type for the strong-negative-MR compositions are extracted only from Hall-effect data above 100 K, because low-temperature Hall data are not considered meaningful. The paper then uses these high-temperature data to claim \"a major transformation in the electronic structure around the x = 0.3 composition\" and links this transformation to the low-temperature negative MR. Since the negative MR develops below roughly 50 K, the high-temperature Hall data do not constrain the low-temperature electronic state; a CDW gap, localization, or other low-temperature reconstruction could invalidate the band-structure narrative. Please either provide low-temperature Hall data or explicitly reframe the claim as a high-temperature observation that is not directly connected to the MR mechanism.","section":"Section III, Fig. 4 and the paragraph on Hall effect"}],"minor_comments":[{"comment":"In the sentence describing field-dependent magnetization, the text refers to \"H⊥ab (Fig. 4c)\" but Fig. 4c is a Hall-effect panel; the out-of-plane magnetization data appear in Fig. 5c. Please correct the cross-reference.","section":"Section III, paragraph after Fig. 5"},{"comment":"The MR is defined with an absolute value, |[ρ(H)-ρ(0)]|/ρ(0). Please specify whether ρ(H) ever changes sign, and report the signed MR so that the low-field positive-MR dip and the high-field negative MR are unambiguously distinguished.","section":"Section III, definition of MR"},{"comment":"The statement that the strong negative MR and low-field dip are \"reproducible in multiple samples\" is not supported by shown data; please include sample-to-sample comparison or error bars on the MR values.","section":"Section II and Fig. 2b"},{"comment":"The title contains a typo: \"off-Stochiometric\" should be \"off-Stoichiometric.\"","section":"Title"},{"comment":"Reference [49] (Xu et al., PRB 92, 205310) is cited for the statement that the nodal-line Dirac crossing near the Fermi energy is protected by mirror symmetry of the P4/nmm lattice, but that reference concerns an oxide topological insulator and does not appear relevant; please verify the citation or replace it with the appropriate symmetry-protection reference for ZrSiS-type materials.","section":"Section III, references"}],"recommendation":"major_revision","confidential_remarks":"The paper is a solid compositional study with an intriguing but not yet fully verified central claim. The absence of symmetrized MR/Hall data is the key load-bearing gap; the required additional measurements are straightforward and within the authors' experimental capabilities, so I recommend major revision rather than rejection. The manuscript also leans heavily on the same group's previous LnSbTe studies, though this is not disqualifying given the topic. The journal should insist on seeing the field-polarity symmetrization data before publication."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear Colleague,\n\nThe paper reports a new composition series PrSbxTe2-x and a 97% negative MR at 2 K and 9 T for x = 0.3. That is a big number, and if it holds it puts this compound next to GdPS, EuTe2, and CeSb0.11Te1.90. The structural work is solid: Rietveld refinements across six compositions, clear tetragonal-to-orthorhombic evolution, and the re-entrant tetragonal phase at low Sb content that so far only NdSbxTe2-x had shown. The magnetization and heat capacity show no long-range order, only anisotropic Pr-localized moments with ferromagnetic correlations along c. The paper is honest that the Hall data for the strong-MR samples are only meaningful above 100 K and that the mechanism is speculative.\n\nThe soft spot is the one that matters. The headline MR is a longitudinal resistivity measurement, and the authors report it using |[ρ(H)-ρ(0)]|/ρ(0) with no mention of averaging +B and -B. In the same paper they say that for these strong-MR samples the Hall contacts pick up an 'inevitable mixture of the longitudinal resistivity component' — meaning their contact geometry is not ideal. If the longitudinal contacts are likewise misaligned, a Hall voltage can ride on top of the resistive signal, and because the Hall term is odd in field, a single-polarity sweep can look like a large drop or rise depending on sign. Given that the zero-field resistivity of this sample is ~50 Ω cm at 2 K and the apparent drop is 97%, the room for a contamination artifact is large. The two-fold angular MR and its persistence across several samples and temperatures make me think the effect is likely real, not raw garbage. But the paper should show R(B) and R(-B) overlapping, or at least state that the field was reversed. That is a fixable experimental detail, and without it the central number is not fully established.\n\nMinor issues: no error bars on any transport or extracted quantity; the carrier-density story leans entirely on high-T Hall data; and the abstract's 'promising platform for device applications' is overreach for an effect at 2 K and 9 T.\n\nVerdict: worth a serious referee, but the referee should ask for symmetrized MR and a sensitivity estimate of contact misalignment. I would not cite the 97% number in my own work until that check appears.","headline":"Plausible new large negative MR in PrSb0.3Te1.7, but the missing field-reversal symmetry check is a real hole in the central claim.","tokens_in":15670,"tokens_out":3225,"would_cite":false,"duration_ms":35890,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"PrSb0.3Te1.7 shows a 97% negative transverse magnetoresistance at 9 T and 2 K, attributed to magnetic-field-driven band restructuring amplified by the strongest orthorhombic distortion in the PrSbxTe2-x series.","keywords":["negative magnetoresistance","topological semimetal","PrSbTe","rare-earth antimony telluride","magnetotransport","orthorhombic distortion","charge density wave","magnetic anisotropy"],"falsifier":"One concrete test is angle-resolved photoemission or high-field magneto-optical spectroscopy on PrSb0.3Te1.7: the band-modification scenario predicts that a perpendicular magnetic field approaching 9 T shifts the bands or closes an existing gap near the Fermi level, visible as a change in the electronic density of states; observing no such change would falsify the proposed mechanism while leaving the raw resistivity drop unexplained by it.","tokens_in":14571,"feed_emoji":"🧲","tokens_out":17131,"duration_ms":134388,"temperature":0.7,"pith_summary":"The paper studies a family of layered rare-earth antimony tellurides, PrSbxTe2-x, in which the Sb:Te ratio tunes the crystal structure. Replacing enough antimony with tellurium converts the tetragonal lattice to an orthorhombic one, with the strongest distortion at $x = 0.3$, and at that same composition the material shows a very large negative transverse magnetoresistance: resistance falls by 97% at 9 T and 2 K when the field is perpendicular to the layers. The effect is accompanied by a two-fold angular anisotropy that mirrors the magnetic anisotropy, even though the material shows no long-range magnetic order down to 1.8 K. The paper argues the negative MR is not the chiral-anomaly effect, because the field is perpendicular to the current, but rather a magnetic-field-driven reshaping of the electronic bands—possibly closing or shrinking a gap—amplified by the unusually strong orthorhombic distortion at $x = 0.3$. If correct, the finding makes PrSb0.3Te1.7 a tunable platform for large magnetoresistance without requiring magnetic order.","feed_headline":"Off-stoichiometric PrSbTe shows 97% negative magnetoresistance","feed_subtitle":"A tellurium-rich composition drops resistance by 97% at 9 tesla, with field-driven band changes proposed.","key_machinery":"The load-bearing object is the specific off-stoichiometric composition PrSb0.3Te1.7 in the orthorhombic Pmmn phase, an orthorhombic crystal structure in which the antimony square nets are distorted; its in-plane lattice distortion—the largest value of $(a-b)/((a+b)/2)$ in the series—coincides with a switch in Hall carrier sign and a minimum carrier density near $\\sim 10^{22}\\,\\mathrm{cm}^{-3}$. The mechanism the paper invokes is a magnetic-field-driven modification of the electronic structure: strong magnetic correlations with two-fold anisotropy couple to the bands through exchange splitting or spin-orbit coupling and shrink or close a gap, possibly a charge-density-wave gap associated with the orthorhombic distortion, so in-plane conduction rises sharply as the field grows. The angular coincidence between the two-fold MR anisotropy and the two-fold magnetization anisotropy is the key experimental evidence that magnetism and transport are linked.","core_discovery":"The central discovery is that PrSb0.3Te1.7, a composition in the topological semimetal family PrSbxTe2-x, exhibits a very large negative transverse magnetoresistance of about 97% at 9 T and 2 K with the field perpendicular to the ab-plane, corresponding to roughly a 3,000% change when normalized to the high-field resistivity. At low fields a small positive MR dip appears below about 1.5 T at 2 K, reminiscent of weak antilocalization, but the dominant high-field response is a sharp resistivity collapse. The paper establishes that this composition has the strongest orthorhombic distortion in the series, that its Hall effect switches from hole-dominated to electron-dominated with a minimum carrier density near $x = 0.3$, and that its magnetic susceptibility is anisotropic with two-fold symmetry but shows no long-range order down to 1.8 K. The angular dependence of the magnetoresistance mimics that two-fold anisotropy, with maximum negative MR for $H\\perp ab$. The authors propose that the negative MR arises from magnetic-field-driven modification of the electronic band structure—likely a reduction or closure of a charge-density-wave-related gap—rather than from the chiral anomaly, which cannot explain transverse negative MR, or from simple spin scattering, which would not be so composition-sensitive.","pith_inferences":["If the band-structure modification picture is right, the MR should come with a field-induced enhancement of the electronic specific heat coefficient gamma or a detectable change in the low-temperature Hall carrier density; this is directly testable on the same crystals.","The re-entrant tetragonal phase at $x = 0.05$, which is tellurium-rich but undistorted, offers a natural control experiment: if its transverse MR is small and positive like the Sb-rich samples, the orthorhombic distortion is the decisive structural ingredient for the large negative MR.","The carrier-density minimum near $x = 0.3$ hints at a Lifshitz-like electronic transition; angle-resolved photoemission across the series could reveal whether a Van Hove singularity or band inversion near the Fermi level is responsible for the sensitivity to magnetic field.","The low-field positive MR dip, resembling weak antilocalization, suggests a tunable crossover field; engineering that dip field by composition could produce a magnetoresistive switch operating at a few tesla."],"forward_implications":["PrSb0.3Te1.7 becomes a concrete platform for studying large negative magnetoresistance in a topological material without long-range magnetic order, with the effect controlled by composition.","The two-fold angular anisotropy of the magnetoresistance, mirroring the magnetic anisotropy, implies that the field direction can tune the resistance by up to roughly 5,800% at 9 T and 3 K.","Composition tuning in the LnSbxTe2-x family can switch hole-dominated to electron-dominated transport while drastically changing carrier density, offering a route to engineer band structures and magnetotransport in related rare-earth compounds.","If the field-driven gap-reduction mechanism is correct, compositions whose orthorhombic distortion or charge-density-wave gap is tuned near the verge of closure could show even larger or higher-temperature negative magnetoresistance.","The low-field positive MR dip reminiscent of weak antilocalization indicates active spin-orbit coupling, a feature that could matter for spintronic device concepts."],"supporting_citations":[{"why":"Reports Dirac nodal-line states in stoichiometric PrSbTe and provides the reference for its structure, absence of magnetic order, and positive magnetoresistance that contrasts with the x = 0.3 composition.","marker":"[40]"},{"why":"Provides the tetragonal crystal structure and electronic-structure data for stoichiometric PrSbTe, used as the baseline for the off-stoichiometric series.","marker":"[41]"},{"why":"Documents an insulator-to-metal transition with extremely large magnetoresistance in structurally similar GdPS, the closest precedent for the proposed field-driven band-modification mechanism.","marker":"[47]"},{"why":"Shows tunable charge density waves and structural transitions in LnSbxTe2-x, supplying the background for the tetragonal-to-orthorhombic evolution and the charge-density-wave gap scenario.","marker":"[57]"},{"why":"Details charge density waves in orthorhombic off-stoichiometric GdSbxTe2-x-delta, supporting the claim that such compositions can host a small or partial gap.","marker":"[63]"},{"why":"Documents the re-entrant tetragonal phase and composition-dependent magnetism in NdSbxTe2-x+delta, used for comparing the structure evolution observed in PrSbxTe2-x.","marker":"[64]"},{"why":"Shows band engineering of Dirac semimetals via charge density waves, cited to support the idea that gap modification can dominate transport.","marker":"[66]"},{"why":"Reports very large negative magnetoresistance in the charge-density-wave regime of the antiferromagnetic Dirac semimetal CeSb0.11Te1.90, the direct precedent for large negative MR in another LnSbxTe2-x composition.","marker":"[70]"}],"fun_headline_variants":["PrSb0.3Te1.7 delivers 97% negative magnetoresistance at 9 T","Tellurium-rich PrSbTe drops resistance by 97% in magnetic field","97% negative MR in topological semimetal PrSb0.3Te1.7","Resistance collapses by 97% in off-stoichiometric PrSbTe"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the high-temperature Hall data (measured above 100 K) faithfully reveal the low-temperature electronic structure around $x = 0.3$; if a gap or localization develops below 100 K that changes the carrier balance, the band-structure explanation for the large negative magnetoresistance would lack support, even though the measured magnetoresistance itself would remain.","fun_headline_variants_meta":{"raw":{"variants":["PrSb0.3Te1.7 delivers 97% negative magnetoresistance at 9 T","Tellurium-rich PrSbTe drops resistance by 97% in magnetic field","97% negative MR in topological semimetal PrSb0.3Te1.7","Resistance collapses by 97% in off-stoichiometric PrSbTe"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000551,"raw_usage":{"total_tokens":2629,"prompt_tokens":945,"completion_tokens":1684,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":561,"completion_tokens_details":{"reasoning_tokens":1590}},"tokens_in":561,"tokens_out":1684,"duration_ms":11329,"temperature":1.0,"reasoning_tokens":1590,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-08T23:09:40.945781+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"One concrete test is angle-resolved photoemission or high-field magneto-optical spectroscopy on PrSb0.3Te1.7: the band-modification scenario predicts that a perpendicular magnetic field approaching 9 T shifts the bands or closes an existing gap near the Fermi level, visible as a change in the electronic density of states; observing no such change would falsify the proposed mechanism while leaving the raw resistivity drop unexplained by it.","supporting_citations":[{"cited_title":"Yuan et al., Observation of Dirac nodal line states in topological semimetal candidate PrSbTe, Phys","cited_arxiv_id":null,"evidence_quote":"Reports Dirac nodal-line states in stoichiometric PrSbTe and provides the reference for its structure, absence of magnetic order, and positive magnetoresistance that contrasts with the x = 0.3 composition."},{"cited_title":"Regmi et al., Electronic structure in a rare-earth based nodal-line semimetal candidate PrSbTe, Phys","cited_arxiv_id":null,"evidence_quote":"Provides the tetragonal crystal structure and electronic-structure data for stoichiometric PrSbTe, used as the baseline for the off-stoichiometric series."},{"cited_title":"Acharya et al., Insulator-to-Metal Transition and Isotropic Gigantic Magnetoresistance in Layered Magnetic Semiconductors, Advanced Materials 27, 2410655 (2024)","cited_arxiv_id":null,"evidence_quote":"Documents an insulator-to-metal transition with extremely large magnetoresistance in structurally similar GdPS, the closest precedent for the proposed field-driven band-modification mechanism."},{"cited_title":"Singha, T","cited_arxiv_id":null,"evidence_quote":"Shows tunable charge density waves and structural transitions in LnSbxTe2-x, supplying the background for the tetragonal-to-orthorhombic evolution and the charge-density-wave gap scenario."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Details charge density waves in orthorhombic off-stoichiometric GdSbxTe2-x-delta, supporting the claim that such compositions can host a small or partial gap."},{"cited_title":"Karki Chhetri, R","cited_arxiv_id":null,"evidence_quote":"Documents the re-entrant tetragonal phase and composition-dependent magnetism in NdSbxTe2-x+delta, used for comparing the structure evolution observed in PrSbxTe2-x."},{"cited_title":"Lei et al., Band Engineering of Dirac Semimetals Using Charge Density Waves, Advanced Materials 33, 2101591 (2021)","cited_arxiv_id":null,"evidence_quote":"Shows band engineering of Dirac semimetals via charge density waves, cited to support the idea that gap modification can dominate transport."},{"cited_title":"Singha et al., Colossal magnetoresistance in the multiple wave vector charge density wave regime of an antiferromagnetic Dirac semimetal, Science Advances 9, eadh0145 (2023)","cited_arxiv_id":null,"evidence_quote":"Reports very large negative magnetoresistance in the charge-density-wave regime of the antiferromagnetic Dirac semimetal CeSb0.11Te1.90, the direct precedent for large negative MR in another LnSbxTe2-x composition."}],"review_version":1}